The present invention relates to subterranean cementing operations, and more particularly to an apparatus useful in loading cementing plugs and darts into tubulars, and methods of using such apparatus in subterranean cementing operations.
Cementing operations may be conducted in a subterranean formation for many reasons. For instance, after (or, in some cases, during) the drilling of a well bore within a subterranean formation, pipe strings such as casings and liners are often cemented in the well bore. This usually occurs by pumping a cement composition into an annular space between the walls of the well bore and the exterior surface of the pipe string disposed therein. Generally, the cement composition is pumped down into the well bore through the pipe string, and up into the annular space. Prior to the placement of the cement composition into the well bore, the well bore is usually full of fluid, e.g., a drilling or circulation fluid. Oftentimes, an apparatus known as a cementing plug may be employed and placed in the fluid ahead of the cement composition to separate the cement composition from the well fluid as the cement slurry is placed in the well bore, and to wipe fluid from the inner surface of the pipe string while the cementing plug travels through it. An apparatus known as a dart also may be used, inter alia, to facilitate deployment of cementing plugs within the well bore, e.g., by contacting a cementing plug in a manner that separates (e.g., shears) a frangible connection holding the cementing plug in place, thereby freeing the cementing plug to travel along the well bore. Other objects (e.g., a ball) also may be used for these and similar purposes. Once placed in the annular space, the cement composition is permitted to set therein, thereby forming an annular sheath of hardened substantially impermeable cement that substantially supports and positions the pipe string in the well bore and bonds the exterior surface of the pipe string to the walls of the well bore.
Conventional methods of placing a cementing plug or dart in a well bore typically involve loading the cementing plug or dart into a tubular, such as the pipe string or a cementing head, either of which may have a cross-sectional area that is smaller than the maximum cross-sectional area of the cementing plug or dart. Commonly, the cementing plug or dart is forced into the tubular by hand until the cementing plug or dart can no longer be moved by hand. Subsequently, an operator may use, e.g., a sledge hammer and rod to further load the cementing plug or dart into the desired position. This may be problematic because it may create safety concerns for the operator, delay the placement in the well bore of the cementing plug or dart (and, consequently, the cement composition), and damage the cementing plug or dart itself.